For the reach tube of a linear time-varying system with ellipsoidal bounds on the control variable consider the following approximation problem. Find a tight ellipsoid-valued tube inside the reach tube that touches it along any prespecified smooth curve on the boundary? We construct this ellipsoidal tube, and show that if the given curve is itself a system trajectory, the tube can be calculated recursively, with minimum computational burden.
Alexander B. Kurzhanski, Pravin Varaiya